Preparation method of carrier type abamectin nano pesticide

Abstract

The invention discloses a preparation method of a carrier type abamectin nano pesticide, and belongs to the technical field of pesticides, the preparation method comprises the following steps: mixing magnesium chloride hexahydrate and aluminum chloride hexahydrate, dissolving in deionized water to prepare a salt solution, adding an ammonia water solution to generate a precipitate, adding a sodium hydroxide solution to adjust the pH value to 10 + / -0.2 to obtain a precipitate, centrifuging, cleaning and drying to obtain the carrier type abamectin nano pesticide. The preparation method comprises the following steps: preparing Mg / Al-LDH sol, adding the Mg / Al-LDH sol into an SDS (Sodium Dodecyl Sulfate) solution, uniformly dispersing, adjusting the pH value to 10 + / -0.2, uniformly stirring, washing and filtering to obtain an LDH NPs nano material, adding the LDH NPs nano material and abamectin into absolute ethyl alcohol, stirring until the absolute ethyl alcohol is completely evaporated, and freeze-drying to obtain the abamectin nano material. Compared with the prior art, the carrier type abamectin nano pesticide prepared by the method has the advantages of higher drug loading capacity, better stability and difficulty in deliquescence, the lasting period of abamectin in soil can be effectively prolonged, and the ecological toxicity to non-target animals is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of pesticides, and particularly relates to a preparation method of a carrier-type abamectin nano-pesticide. Background Art

[0002] Abamectin (AVM) is a class of macrolide antibiotics produced by Streptomyces avermitilis through liquid fermentation. It has broad-spectrum insecticidal and acaricidal properties and is mainly used in crops for the control of pests, nematodes and mites. Its application methods include spraying, punching injection, furrow application and hole application. Because of its high efficacy, convenient application, the ability to kill nematodes, insects and mites, and its relatively stable nature as an antibiotic insecticide, it is favored by pesticide production enterprises and farmers.

[0003] Currently, the dosage form of the registered abamectin nano-pesticide on the market is generally microcapsule suspension. However, the carrier and the active ingredient of this dosage form of abamectin nano-pesticide will separate during long-term storage, resulting in a rapid decrease in the drug loading amount and failing to achieve the sustained-release effect. In addition, due to the properties of conventional abamectin pesticides such as easy photolysis, hydrolysis and microbial degradation, the utilization rate of abamectin pesticides will be reduced during use. Therefore, selecting a suitable nano-sustained-release carrier to construct a carrier-type abamectin can not only solve the stability of abamectin in the environment, improve the utilization rate of pesticides, but also reduce the number of pesticide applications and the environmental pollution by virtue of the sustained-release effect of the nano-carrier, achieving "reduction in quantity and increase in efficiency" in the true sense.

[0004] The nano-pesticide carrier technology mainly solves two problems existing in pesticides. One is to reduce environmental pollution. Hydrophobic pesticides need to be prepared into suitable dosage forms to improve their water solubility, while traditional dosage forms contain a large amount of adjuvant components, and a large amount of adjuvant components will cause serious pollution to the environment. The other is to improve the utilization rate of pesticides and protect pesticides that are extremely vulnerable to photolysis, hydrolysis and microbial degradation. Therefore, for pesticides like AVM that have both hydrophobic properties and easy decomposition properties, it is urgent to prepare a suitable nano-carrier to reduce the negative effects on the environment while improving the stability of pesticides.

[0005] There have been reports on layered hydroxide carrier-type abamectin nano-pesticides in the prior art, but there are problems such as low drug loading amount and easy deliquescence of the prepared samples. Summary of the Invention

[0006] The purpose of the present invention is to solve the deficiencies of the prior art and provide a preparation method of a carrier-type abamectin nano-pesticide. The carrier-type abamectin nano-pesticide prepared by this method has a relatively high drug loading amount and good stability, can effectively avoid the influence of factors such as photolysis and hydrolysis in the environment, and prolongs the effective period of abamectin in the soil.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A preparation method of a carrier-type abamectin nano-pesticide, comprising the following steps:

[0009] (1) Add magnesium chloride hexahydrate and aluminum chloride hexahydrate to deionized water, stir and dissolve to obtain a salt solution;

[0010] (2) Add an ammonia water solution to the salt solution to form a precipitate, and then add a sodium hydroxide solution to adjust the pH to 10 ± 0.2 to obtain a precipitate;

[0011] (3) Let the precipitate stand and then centrifuge, wash with deionized water and dry to obtain a Mg / Al-LDH sol;

[0012] (4) Add the Mg / Al-LDH sol to an SDS (sodium dodecyl sulfate) solution, disperse evenly, then adjust the pH value to 10 ± 0.2 with a sodium hydroxide solution, stir evenly, wash, and filter to obtain LDH NPs nano-materials;

[0013] (5) Add the LDH NPs nano-materials and abamectin to absolute ethanol, stir until the absolute ethanol is completely evaporated, and then freeze-dry to obtain a carrier-type abamectin nano-pesticide.

[0014] Further, in step (1), the molar ratio of the magnesium chloride hexahydrate to the aluminum chloride hexahydrate is 2:1.

[0015] Further, in step (3), the drying temperature is 80 °C and the time is 24 h.

[0016] Further, in step (4), the concentration of the SDS solution is 0.1 mol / L.

[0017] Further, in step (5), the mass ratio of the LDH NPs nano-materials to abamectin is 1:(1.2 - 1.8).

[0018] Further, in step (5), the freeze-drying temperature is -30 °C to -40 °C and the time is 24 h.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1) The present invention provides a preparation method of a carrier-type abamectin nano-pesticide. The carrier-type abamectin nano-pesticide prepared by this method has a high drug loading amount and is not easy to deliquesce.

[0021] 2) The carrier-type abamectin nano-pesticide of the present invention doubles the soil persistence period while reducing the ability of earthworms to accumulate the active ingredient of abamectin (the accumulation of the active ingredient of abamectin by earthworms is reduced by 35% compared to the original abamectin), thereby reducing the ecological toxicity to non-target animals.

[0022] 3) The LDHs-AVM nano-pesticide constructed in the present invention exhibits remarkable effects in terms of low cost, slow-release effect, and low toxicity compared to the registered abamectin pesticides. Description of the Drawings

[0023] Figure 1 TEM and SEM images of the carrier-type abamectin nano-pesticide prepared in Example 1;

[0024] Figure 2 XRD pattern of the carrier-type abamectin nano-pesticide prepared in Example 1;

[0025] Figure 3 Degradation curves of AVM original drug and the carrier-type abamectin nano-pesticide LDHs-AVM prepared in Example 1 in artificial soil;

[0026] Figure 4 Enrichment and elimination curves of AVM original drug and LDHs-AVM nano-pesticide in earthworms. Detailed Embodiments

[0027] The technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0028] In the embodiments of the present invention, the experimental methods, unless otherwise specified, are all conventional methods in the art.

[0029] Example 1

[0030] A preparation method of a carrier-type abamectin nano-pesticide, comprising the following steps:

[0031] (1) Add 4.04 g of magnesium chloride hexahydrate and 2.4 g of aluminum chloride hexahydrate to 50 mL of deionized water, stir and dissolve to obtain a salt solution;

[0032] (2) Add 6 mL of ammonia water to 94 mL of deionized water to obtain an ammonia water solution with a volume concentration of 6%, add it to the salt solution obtained in step (1), precipitate will form, then add sodium hydroxide solution to adjust the pH value to 10 ± 0.2 to obtain a precipitate;

[0033] (3) After allowing the precipitate to stand in the mother liquor for 45 min, centrifuge it at 3000 rpm for 5 min. After washing with deionized water, store the precipitate in a glass bottle and dry it in an oven at 80 °C for 24 h to obtain the Mg / Al-LDH sol;

[0034] (4) Add the Mg / Al-LDH sol to 50 mL of a 0.1 mol / L SDS (sodium dodecyl sulfate) solution. After dispersing it evenly, adjust the pH value to 10 ± 0.2 using a sodium hydroxide solution, stir evenly, wash, and filter to obtain the LDHNPs nanomaterial;

[0035] (5) Add 1 g of the LDH NPs nanomaterial and 1.56 g of abamectin (96% purity) to 100 mL of absolute ethanol. Stir until the absolute ethanol completely evaporates, and then freeze-dry at -35 °C for 24 h to obtain the carrier-type abamectin nano-pesticide, denoted as LDHs-AVM.

[0036] Figure 1 Figures 10 and 11 are the TEM and SEM images of the carrier-type abamectin nano-pesticide prepared in Example 1, where Figure 1 a is the TEM image of the original drug abamectin, Figure 1 b is the TEM image of the carrier-type abamectin nano-pesticide prepared in Example 1, Figure 1 c is the SEM image of the carrier-type abamectin nano-pesticide prepared in Example 1. It can be seen that the morphology of the AVM original drug is in the shape of large stones, with sizes between 56 μm and 100 μm, belonging to the micron scale; the carrier-type abamectin nano-pesticide prepared in Example 1 has a layered and flaky structure, with sizes between 64.7 nm and 96.8 nm, belonging to the nanoscale; at the same time, according to the scanning electron microscope image (SEM), it can be clearly seen that the LDHs-AVM nano-pesticide belongs to the hexagonal and six-sided flaky morphology. In addition, there is no stone-like structure of the AVM original drug in the morphological field of view of the carrier-type abamectin nano-pesticide. At the same time, the hybridized nano-pesticide conforms to the morphological characteristics of the LDHs nano-carrier type structure and the size conforms to the nano-size, indicating that the carrier-type abamectin nano-pesticide is successfully prepared.

[0037] Figure 2 Figure 12 is the XRD pattern of the carrier-type abamectin nano-pesticide prepared in Example 1. As can be seen from the figure, the LDH NPs nano-carrier and the LDHs-AVM nano-pesticide contain all the characteristic diffraction peaks of hydrotalcite, indicating that the sample has a good crystal structure, and the main phases are identified as Mg 2 Al 2 (OH) 18 、[Mg 5 Al 3 (OH) 16 [(OH) 3 (H 2O) 4 , NaCl. The crystal particle size of the channels of LDH NPs nanocarriers and LDHs-AVM nano-pesticides was calculated using the Scherrer formula D = Kλ / (βcosθ) in Jade software. 003 The crystal particle size of the d 003 channel layer spacing of LDH NPs nanocarriers is between 7.3 nm and 7.9 nm, while the d 003 channel layer spacing of LDHs-AVM nano-pesticides after loading avermectin expands to between 9.3 nm and 11.0 nm, indicating that the layer spacing of LDHs nanocarriers increases and avermectin molecules are inserted.

[0038] 1. Test the slow-release performance of the carrier-type avermectin nano-pesticide (LDHs-AVM) prepared in Test Example 1.

[0039] Experimental method: First, prepare a 1000 mg / kg avermectin stock solution for later use. Take 0.02 g of LDHs-AVM nano-pesticide and dissolve it in methanol, sonicate for 5 minutes to completely release avermectin. Take 1 ml of the solution, dilute it with methanol, and filter it through a 0.22 μm filter membrane to prepare a sample to be detected. Use the 1000 mg / kg avermectin stock solution to dilute it into standard products with concentration gradients of 0.5 mg / kg, 1 mg / kg, 2.5 mg / kg, 5 mg / kg, 10 mg / kg, 15 mg / kg, and 20 mg / kg respectively, and obtain the avermectin standard curve y = 0.415x - 0.734. Calculate the drug loading of LDHs-AVM according to the drug loading formula:

[0040] Drug loading = mass of avermectin in LDHs-AVM nano-pesticide / mass of LDHs-AVM nano-pesticide * 100%

[0041] After calculation, the drug loading of LDHs-AVM is 62%.

[0042] 2. Conduct an enrichment and elimination experiment on AVM original drug and the LDHs-AVM nano-pesticide prepared in Example 1 in soil and earthworms.

[0043] Experimental materials: The earthworms used in the experiment are healthy earthworms with reproductive rings (body weight 0.6 g - 0.8 g) purchased from Tianjin Liyuan Environmental Protection Technology Co., Ltd.; the soil used in the experiment is artificial soil, composed of 70% sand, 20% kaolin, and 10% sphagnum moss by mass fraction.

[0044] Experimental method: Earthworms that had their intestines cleared overnight for 12 hours were respectively exposed to artificial soil containing 4 mg / kg of AVM technical and LDHs-AVM nano-pesticide, and the AVM concentration in the earthworms was detected, which was the earthworm enrichment experiment. On the second and third days respectively, the earthworms exposed to AVM technical and LDHs-AVM nano-pesticide were transferred to clean artificial soil, and the AVM concentration in the earthworms was detected, which was the earthworm dissipation experiment. Meanwhile, the active ingredients of avermectin in the artificial soil were analyzed. The specific sampling times are as follows:

[0045] In the enrichment experiment, earthworm samples were collected at time points of 0 d, 2 d, 3 d, 4 d, 6 d, 7 d, 9 d, and 10 d. In the dissipation experiment, earthworm samples were collected at time points of 0 d, 1 d, 2 d, 3 d, 4 d, 11 d, and 18 d after being transferred to clean artificial soil. Meanwhile, artificial soil with earthworm exposure was collected at 0 d, 4 d, 6 d, 7 d, 9 d, 10 d, 12 d, 13 d, 14 d, and 21 d. The above samples were subjected to extraction and detection of the active ingredients of avermectin.

[0046] Method for detecting the AVM concentration in soil samples and earthworm samples:

[0047] The QuEChERS method was used for the pretreatment of soil samples and earthworm samples. 5 g of the above-exposed soil or earthworms were respectively added to 25 mL of acetonitrile extraction solution in a 50 mL centrifuge tube for standby. Subsequently, centrifugation was carried out at 4000 rpm for 15 min to separate the acetonitrile layer from the mixture, and it was washed with anhydrous sodium sulfate. The soil and earthworm samples were extracted with acetonitrile. Subsequently, N-propylethylenediamine (PSA) and octadecylsilane (C18) purifying agents were used to remove pigments and oils in the soil and earthworm matrices. Then, rotary evaporation was carried out at 40 °C. The soil samples were directly eluted with 1 mL of acetonitrile and then passed through a 0.22 μm filter membrane into a dry brown injection vial for subsequent analysis. The earthworm samples were rotary evaporated at 40 °C until 1 mL of solution remained. The liquid-liquid extraction method was needed to remove the excess oil in the earthworms. An additional volume of n-hexane (1 mL) was added to the system, and after balancing and mixing evenly, the upper layer liquid was taken and continued to be rotary evaporated at 40 °C. Finally, it was eluted with 1 mL of acetonitrile and then passed through a 0.22 μm filter membrane into a dry brown injection vial for subsequent analysis.

[0048] The extracted soil samples and earthworm samples were detected on a UPLC-MS / MS instrument (Agilent Technologies, Santa Clara, CA, USA). A Poroshell PFP chromatographic column (2.1×100 mm, 2.7 μm particle size, Agilent) was used, and 95% acetonitrile and 5% water (containing 0.3% formic acid) were used as the mobile phase to separate AVM. The injection volume was set to 5.0 μL and the flow rate was 0.3 mL / min on the UPLC-MS / MS instrument. The specific mobile phase gradient is shown in Table 1. All test samples were subjected to three replicate experiments.

[0049] Table 1 Mobile phase gradient for HPLC-MS / MS instrument analysis

[0050]

[0051] To verify the correctness of the detection method, the spiked recoveries and relative deviations of LDHs-AVM nano-pesticide in soil and earthworm tissues were tested at different spiked concentrations (0.5 mg / kg, 1 mg / kg, and 5.0 mg / kg). The test results are shown in Table 2:

[0052] Table 2 Spiked recoveries and relative deviations of LDHs-AVM nano-pesticide in soil and earthworm tissues

[0053]

[0054] As can be seen from Table 2, at spiked concentrations of 0.5 mg / kg, 1 mg / kg, and 5.0 mg / kg, the spiked recoveries of LDHs-AVM nano-pesticide in soil and earthworm tissues were between 97.82% and 105.19%, and the relative deviations were between 1.49% and 3.11%. The degradation curves of LDHs-AVM nano-pesticide in soil and earthworm tissues conform to the first-order degradation kinetic equation, and the fitting curve R 2 was between 0.98 and 0.99. This indicates that this method is applicable to the extraction of LDHs-AVM nano-pesticide in soil and earthworm tissues, and the analytical method meets the pesticide residue standards.

[0055] The half-lives of LDHs-AVM nano-pesticide and AVM technical in artificial soil were analyzed using the above UPLC-MS / MS instrument detection method. The degradation curves of LDHs-AVM nano-pesticide and AVM technical in soil both conform to the first-order kinetic model. According to the formula C = C 0 e -Kt the reaction rate constant k was calculated, where C o is the initial concentration, which is 4 mg / kg, and C is the concentration at different time points. The half-life (T 1 / 2 ) formula T 1 / 2= In 2 / k = 0.693 / k, where T 1 / 2 is the time required for the initial concentration to decrease by 50%. The specific degradation parameters are shown in Table 3. The initial concentration of the soil was set to 4 mg / kg (0.4 ml of LDHs-AVM nano-pesticide and AVM original drug with a concentration of 1000 mg / kg were added to 100 g of artificial soil respectively). Relative to the degradation rate of AVM original drug in the soil (T 1 / 2 : 1.83 days), the degradation rate of LDHs-AVM nano-pesticide (T 1 / 2 : 3.45 days) was significantly slower (p < 0.05), indicating that avermectin after loading on the LDHs carrier had an obvious slow-release effect in the soil ( Figure 3 ).

[0056] Table 3 Degradation parameters of LDHs-AVM nano-pesticide and original drug avermectin in the soil

[0057]

[0058] The formula for the bioconcentration factor (BSAF) = Ce / Cs, where Ce is the concentration of AVM enriched by earthworms from the soil and Cs is the concentration of AVM in the soil. The calculated BSAF values indicate that earthworms have a stronger ability to enrich and eliminate the original drug AVM relative to LDHs-AVM nano-pesticide. As shown in Table 4 below:

[0059] Table 4 Bioconcentration factor values of earthworms for LDHs-AVM nano-pesticide and original drug AVM

[0060]

[0061] The research results in Table 4 prove that there is an enrichment effect of both LDHs-AVM nano-pesticide and original drug AVM in earthworms, providing a solid preliminary basis for the later detailed study of the differences in the enrichment and elimination behaviors and chronic toxicity of LDHs-AVM nano-pesticide and original drug AVM in earthworm tissues.

[0062] Table 5 shows the enrichment and elimination of original drug AVM and LDHs-AVM nano-pesticide in earthworms, Figure 4 and is the enrichment and elimination curves of original drug AVM and LDHs-AVM nano-pesticide in earthworms.

[0063] Table 5 Enrichment and elimination of original drug AVM and LDHs-AVM nano-pesticide in earthworms

[0064]

[0065] From Table 5 and Figure 4It can be seen that compared with the AVM technical material, earthworms preferentially accumulate LDHs-AVM nano-pesticides. This phenomenon is due to the small size effect of nano-pesticides, which makes it easier to enter the earthworms through the epidermis and ingestion. Interestingly, the concentration of AVM technical material accumulated by earthworms is significantly higher than that of LDHs-AVM nano-pesticides. The peak concentrations of LDHs-AVM nano-pesticides and AVM technical material accumulated by earthworms in artificial soil are 1.215 mg / kg and 2.768 mg / kg, respectively. This phenomenon indicates that even though the small size effect of nano-pesticides makes it easier to enter earthworms, the LDH NPs nano-carrier may affect the feeding function of earthworms and reduce the ability of earthworms to accumulate LDHs-AVM nano-pesticides. In addition, abamectin loaded with LDHs carriers has a slow-release effect, indicating that the degradation of abamectin in soil and its elimination in earthworms are both slow.

[0066] Through the comparative analysis of the enrichment and elimination experiments of LDHs-AVM nano-pesticides and AVM technical material in soil and earthworms, the present invention clarifies the enrichment and metabolic differences between LDHs carrier-based nano-pesticides and technical materials in the soil-earthworm system. The main conclusions are as follows:

[0067] (1) First, Mg / Al-type LDHs nano-carriers were successfully prepared by co-precipitation. This carrier can effectively intercalate abamectin, and LDHs-AVM nano-pesticides can be successfully obtained.

[0068] (2) The QuEChERS method was used to successfully establish a detection method for LDHs-AVM nano-pesticides and AVM technical material in soil and earthworms. The degradation curves conform to the first-order kinetic model y 阿维菌素 = 8.4375e -0.379x and y LDHs-AVM = 5.9005e -0.201x , and the R 2 values of both are greater than 0.99.

[0069] (3) The half-life of LDHs-AVM nano-pesticides in soil is twice that of AVM technical material, indicating that the successfully constructed nano-pesticides have a significant slow-release effect in soil, reducing the degradation rate of abamectin in soil. In practical applications, the application rate of abamectin can be reduced to achieve a real pesticide reduction strategy.

[0070] (4) According to the BSAF experiment, compared with the LDHs-AVM nano-pesticide, earthworms have a stronger ability to enrich the AVM original drug, and the maximum concentration of the AVM original drug enriched is 2.27 times that of the maximum concentration of the LDHs-AVM nano-pesticide, indicating that the process of earthworms enriching the LDHs-AVM nano-pesticide is hindered, reducing their ability to enrich nano-pesticides. Even so, due to the slow-release effect of the LDHs-AVM nano-pesticide, during the elimination experiment from 14 days to 30 days, the active ingredient of the LDHs-AVM nano-pesticide detected in earthworms is higher than that of AVM.

Claims

1. A method for preparing a carrier-type avermectin nanopesticide, characterized in that: The steps include: (1) adding magnesium chloride hexahydrate and aluminum chloride hexahydrate into deionized water, stirring and dissolving them to obtain a salt solution; (2) adding an ammonia solution to the salt solution to generate a precipitate, and then adding a sodium hydroxide solution to adjust the pH value to 10±0.2 to obtain a precipitate; (3) allowing the precipitate to stand and then centrifuging, washing with deionized water and drying to obtain a Mg / Al-LDH sol; (4) adding Mg / Al-LDH sol to SDS solution, dispersing evenly, adjusting the pH value to 10±0.2 with sodium hydroxide solution, stirring evenly, washing, filtering, and obtaining LDHNPs nanomaterials; (5) Add LDH NPs nanomaterials and avermectin into anhydrous ethanol, stir until the anhydrous ethanol is completely evaporated, and then freeze-dry to obtain a carrier-type avermectin nanopesticide.

2. The method for preparing the carrier-type avermectin nanopesticide as claimed in claim 1, characterized in that: The molar ratio of the magnesium chloride hexahydrate to the aluminum chloride hexahydrate is 2:

1.

3. The preparation method of carrier-type avermectin nanopesticide as claimed in claim 1, characterized in that, In step (3), the drying temperature is 80° C. and the drying time is 24 hours.

4. The method for preparing the carrier-type avermectin nanopesticide as claimed in claim 1, characterized in that: In step (4), the concentration of the SDS solution is 0.1 mol / L.

5. The method for preparing the carrier-type avermectin nanopesticide as claimed in claim 1, characterized in that: In step (5), the mass ratio of the LDHNPs nanomaterial to avermectin is 1:(1.2-1.8).

6. The method for preparing the carrier-type avermectin nanopesticide according to claim 1, characterized in that: In step (5), the freeze-drying temperature is -30°C to -40°C, and the time is 24 hours.

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